REVIEW: Guildford Geology Walk
By Sarah-Jane Kelland, ERCL Ltd
I have always felt privileged growing up as a geologist in the UK, with such varied geology developed over such a tiny island, but who would have imagined the stories that the building stones close to our group meeting place would tell?
On a cool, dry May evening to celebrate our 21st birthday, 40 members of the PESGB Surrey Branch set off to walk a 1.5km route from the White House Pub to Guildford High Street and back. One group led by building stone guru Bob Leppard, and the other by Maurice Curry and Sarah-Jane Kelland. This short sojourn through Guildford town centre covered 500 million years of stratigraphy and all three types of rock, from the Ordovician Borrowdale volcanic ash-fall tuffs fronting ‘Boss’ to the beautiful cream-colored Travertine precipitated from Quaternary mineral hot springs at ‘Barbour’. What to the unsuspecting shopper was merely a walkway was to us a pavement of Carboniferous Millstone Grit Yorkstone flags showing beautiful linguoidal ripples. The granite setts we traversed to cross the road, were an igneous petrologist’s dream of different coloured and textured granites. There were even porphyritic granites with xenoliths present in the granite flags of Angel Lane, worn by the metal rims of horse-drawn carriages.
Slowly snaking past Labradorite fascias with silky Schiller lustre, white Carrara marbles and crossing Serpentinites from ophiolites, we found ourselves back on Continental Crust at the top of the High Street. Here, at Holy Trinity Church we climbed steps constructed from the freshwater Lower Cretaceous Purbeck Limestone, where it is impossible not to walk on gastropod shells, so abundant were they here. Squeezing into the little graveyard behind the church, we admired the only remaining part of the original church with window surrounds of honey-coloured Upper Jurassic Oolitic limestone, set into an external wall with an exquisite chequerboard pattern of Upper Cretaceous flints and well-cemented Eocene Sarsen sandstones. Text-book graded bedding was evident but sadly their presence not understood by the stone mason due to them being laid upside down!
If Jurassic and Cretaceous marine transgressions are your thing, then Abbot’s Hospital is the place for you to visit. Window surrounds made from the marine Upper Jurassic Oolitic limestone, fronted by a balustrade made of marine Upper Jurassic Portland Stone with shelly lags, moving up in time to a paving slab surround of Lower Cretaceous fresh water Paludina Limestone (Weald Marble), full of the gastropod Viviparis paludina.
We may be the oldest and largest branch, but we are always keen to gain new members. The walk went part way there with the usual interest from the public as to why we were touching the walls of shop fronts and spraying them with water. Two Thames Water workmen happily stopped their pneumatic drilling and listened in to what Bob was saying in case it helped with their job. The Master at Abbot’s Hospital also came out to see why so many people were inspecting its masonry, as well as a local homeless man who told us he liked rocks and seemed pleased of some company in the evening air.
Thank you very much to everyone who attended and made it all the more enjoyable with your questions. I am also very grateful to Maurice Curry for seeding the idea of a geology walk, Bob Leppard for his geological knowledge of building stone and for the generous sponsorship of Energy Key Facts, Spectrum and Working Smart for providing food on our return to the pub.